1. Field of the Invention
This invention relates to a crystalline polymer composition and more particularly to a crystalline polymer composition containing 100 parts by weight of a crystalline polymer and 0.005 to 5 parts by weight of a compound represented by formula (I) hereinafter described having a chlorine content of 500 ppm or less.
2. Description of the Related Art
Crystalline polymers, such as polyethylene, polypropylene, polybutene-1, polyethylene terephthalate, polybutylene terephthalate, and polyamide, are slow in crystallization after heat molding and therefore have a low molding efficiency and need mold cooling. Further, they undergo mold shrinkage on crystallization. Furthermore, moldings of these crystalline polymers tend to have insufficient strength or poor transparency due to large crystals formed.
It is known that all these drawbacks are attributed to the crystallinity of the polymers and could be eliminated by increasing the crystallizing temperature of the polymers so as to produce fine crystals rapidly.
Addition of a nucleating agent or a nucleation accelerator is known effective for this purpose. Conventionally used nucleating agents or nucleation accelerators include carboxylic acid metal salts, such as aluminum 4-t-butylbenzoate and sodium adipate, acid phosphoric esters, such as sodium bis(4-t-butylphenyl)phosphate and sodium 2,2'-methylenebis(4,6-di-t-butylphenyl)phosphate, and polyhydric alcohol derivatives, such as dibenzylidene sorbitol and bis(methylbenzylidene) sorbitol.
Of these known compounds, metal salts of a cyclic phosphate of an alkylidenebisphenol disclosed in Japanese Patent Laid-Open Nos. 1736/83 and 184252/84, etc. are particularly effective and have been used widely. However, their effects are still sometimes insufficient, and cases are met with in which an alkali metal chloride is dissolved out in the polymer to cause surface roughness or voids, which are problematical in the practice.